Differential backstop for conveyers, elevators, etc.



, Aug. 21, 194s.v P, A, SMWH 2,383,276'

DIFFERENTIAL BACKSTOP FOR CONVEYERS, ELEVATORS, ETC

Filed July :51, 1944 v5 Sheets-Sheet l v Rg/1. eFH/7W,

Aug. 2l`, 1945. P, A. SMITH 2,383,276

' 4DIFFERENTAL BACKSTOP FOR CNVEYERS, ELEVATORS, ETC

` Filed .July 31, 1,944 s sheets-sheet '2 .infn Il' y I /0404 Sfr/ry.; A

Aug. 2l, 1945. 4 p, A; sMlTH 383,276

DIFFERENTIAL BAcxsToP FOR coNVEYERs, ELEVATQRS, ETC

Filed July 3l, 1944 3 Sheets-Sheet 5 fsf-4! l 10m/z.4 'Sly/rif. I

Patented Aug. 21, 1945 i 2,383,276 i "DIFFERENTAL` BAoKsToP FoR 00N- vEYE-Rs, ELEVATORS, ETC.

Paul A. smith, Aurora, In., assignorto Barber- Greene Company, Aurora, Ill., a .corporation of Illinois 1 Application July 31, 1944,"Serial No. 5477,"158` 2 claims. (01. ics-82) Thisin'vention relates to improvements `in a differential backstop for conveyers, elevators, etc., and more particularly to` aA backstop braking mechanism to prevent conveyers, elevators, and equipment of the same general vcharacter from moving backwards by virtue of the load thereon when forward motion is stopped, although the invention may have other uses and purposes as will be apparent to one skilled in the art.

In the past, many and various differential backstops, band brakes, and thelike have been developed for preventing back-run in the eventthe motive power isshut off while the ascending run of an elevator `or conveyor is loaded. Such devices havebeen` used upon both vertical and inclined elevators, endless conveyers and similar equipment. Heretofore, however, in all instances of which I am aware, the `frame of a` machine, that is, the conveyer or elevator or whatever the machine may be,carried not only the torque load during braking `but also provided the reactive forc opposite to theactive braking force. other words, where a band brake was used as a backstop, the loadforces on the brake band were transmitted to the supporting frameof the ma-` chine in addition to the torque load. This was especially on ratherlightweight portable equipment. Another objectionable feature to devices ofthis character heretofore known is the lack of anysafety factor so far as the brake band is ccncerned, that is, if the brake band lining became` worn, there Wasnothing in addition to help the :braking operation other than the Worn brakel band. l

`With the foregoing in mind, it is an important object of the instantinvention to provide an'automatic differential backstoparranged to divorce the brake load from'the machine withwhich the vide highlyeffective braking with lighter external h loads, which is particularly advantageous on lightly constructed equipment suchas portable installed. i y

which is so arranged that the `reactive force ref" h sulting from the pull on the brake band is utilized` to provide additional braking effort;

l Also a feature of the invention resides in the `provision of a diierential backstop including` aV brake drum and a brake band, so arranged that the reactive `force resulting from a braking vpull on `thebrake band is brought back to thebrake drum by way of a brake shoe. y

in which the reaction to apull on thebralce band presses the shoe into engagement with `the drum, It is a still further object of the instant inven`` tion to Alprovide a dilerential backstop ybraking mechanism which, with the exception of the brake drurrnis connected t0 the machine withwhich it isassociated only at a single pivot point, and` which is very easily and simple adjusted `"when braking effect and yet be economical in construcl tion and use and relatively light in weight.

While some of the more salient features, char--v acteristics and advantages ofthe instant invention have been above pointed out, others will become apparent from the following disclosures, taken in conjunction with the accompanying drawings,` in.`

which VFigi-1re 1 is a fragmentary side elevational viewA of` a differentialfbackstop mechanism embodyingl principles ofthe instant invention, `shcxwingthe l same associated with endless conveyerwelevator equipment, such equipment being indicated dia` grammatically in the drawings;

Figure 2 isfa iragmentary'transversevertical sectional view, with parts in elevationftaken substantially as indicated bythe line lIII lof Fig-f h ure l, looking in the direction of the arrows;

It is also an objectof this invention to proi vide a differentialbackstop so arranged that all forces except the torque load are kept free of themachine or its frame, and all these forces are utilizedin effective braking, both as to the active and reactive forces.`

`,It is also a feature of this invention to provide a differential backstopincluding a brake drum upon whichboth a` brakeband and a brake shoe` vention is shown associated witha material ele` Figure. 3 is an enlarged `l,ragmentary eleva'-` tional view, with parts shown in `section,` of` a` portion of the braking mechanism seen in Fig` ures 1 and 2, showing the same withthe braking means in released position; and n h Figure fl is aA view similar to Figure 3, butillus` trating the braking means in braking position.`;`

As shown on the drawings: h The illustrated embodiment oi` the instant invating machine, illustrated diagrammatically,

including a transverse head shaft I carried inl a "suitable bearing support `2.v i vided with a conveyer drive element 3 which opi` crates an endless bucket conveyer 4. `As the" conveyor is viewed in Figure l, the shaft I ro` tates counter-clockwise for the "conveyer f to* ele` vatematerial. The `frame structure `fol-th'e shaft is pro- Afurther feature of the invention resides `in the provision of a differential backstop involving `ai brake drum, a brake band, and a brake shoe, and

' shank of the bolt I5.

' elevating machine is not illustrated with a single exception of the part most intimately associated with the instant backstop invention. Such portion of the frame structure includes a transverse supporting beam 5, as seen in Figure 1.

It will beI appreciated that when the conveyer mechanism is in operation, and the ascending buckets are loaded with material, -if for any reason the motive power should becut olf, the weight of material in those buckets tends to cause a back-run f the conveyer. vention is, of course, .designed to automatically prevent any such back-run.

The braking mechanism includes a brake drum 6 mounted on an extended end of the shaft I and keyedor otherwise secured to the shaftfor rotation therewith. Braking means lincluding both a brake band and a brake shoe tobe hereinafter described act upon the drum 6 whenever the shaft I tends to move in a reverse direction.

The braking mechanism includes an arm 1' pivoted as indicated at 8 to an anchor bracket 9 mounted upon the aforesaid frame member 5. This is the only connection to the frame of the elevating machine of the braking mechanism acting upon the drum 6. A set screw I0 extending through the horizontal flange of the bracket 9 abuts the underside of the arm land provi-des a downward limit for the pivotal movementof the arm. The arm 1 may be of one integral construction throughout its length, or fabricated from initially separate pieces as illustrated. `In the selected showing, side members II and I 2, each of which is bent as indicated at I3, are attached to the arm 1 by means of bolts I4 or in 'I'he composite,

assaave The present in- 8 and a bifurcated forward portion including the furcations I I and I2, seen in Figure r2.

Extending through the furcations II and I2 in atransversedirection is a headed bolt I5 with which a nut I6 is associated outside the furcation or member I I. is a spacer sleeve I1 which has fixed thereto as by welding, brazing, or an equivalent operation, the carrying portion I8 of a brake shoe4 I9. When the nut I6 is loosened, the brake shoe and spacer sleeve I1 are free to pivot around the The brake shoe may be provided with a suitable lining for frictional contact with the drum 6.

Around the end portions of the spacer sleeve I1, but spaced inwardly from the extreme ends of this sleeve, are bearing members 2I and 22 provided `with circumscribing spacer collars 23 and 24, respectively (Figure 2). It will be noted that each such bearing member together with its spacer collar is disposed sufficiently inwardly from the respective ends of the sleeve I1 so that.

these bearing members will not be squeezed between the furcations I I and I2 when the nut I6 is tightened on. the bolt I5. Pivotally disposed on the bearing member 2I is a bell crank plate 25, and a like plate 26 is pivotally disposed on the bearing member 22. It will be noted with reference to Figures l, 3 and 4 that the plates 25 and 26 are pivoted at what may be termed their elbows. .c

The bell crankplates and 26'jointly hold the ends of a brake band 21 extending around the aforesaid druml 6, which brake band may be lined with `any suitable material as indicated at 28. One end of the brake band is formed into a loop 29 engaged around a spacer sleeve 30 freely sur- Around the shank of the bolt I5 rounding the shank of a bolt 3| extending through the plates 25 and 26 and locked by a suitable nut 32. Suitable washers may be used at each end of the spacer sleeve 3D, if so desired. The other end of the brake band is formed into a loop 33 divided in its central portion as indicated at 34 to permit the ring of an eyebolt 35 to extend between the portions of the loop, and lthese portions are engaged over a pin 36 extending through the ring of the eyebolt. The shank of the eyebolt 35 extends through a polygonal pivot shaft 31 disposed transversely between the bell crank plates 25 and Z6,and having rounded end portions 38 journalled in the plates themselves. The plates 25 and 26 are held in the proper degree of spacing adjacent the polygonal shaft 31 by means of a suitable through bolt and nut arrangement 39 with a spacer sleeve 4I'IA around the shank of the bolt between the plates. This arrangement plus the bolt 3| with the sleeve 30 around the shank thereof maintain` thev plates 25 and 26 in fixed position relatively `to each other. These plates must therefore pivot-inf unison during operation of the braking mecha-V msm.

The brake band 21 is preferably a truly formed band so that even when it is in the released position it hugs the brake drum 6 to some extent. Preferably, it should hug the brake drum `when in released position to just a suflicient extent toY cause a locking of the braking mechanism when the drum tends to rotate in the opposite direction. Means are provided, therefore, to limit the amount of release movement of the brake band. Ihese means include an upstanding bolt 4| havinglits inner end welded 0r otherwise securedto a sleeve` 42 surrounding the shank of a rshaft 43 carried by the outer ends of the furcations II and. It. The bolt extends obliquely upwardly from `between the furcations substantially parallel to the adjacent portion of the brake band 21. The shank of the bolt is provided with a pair of spacednuts 44 and 45 adjustable to define the correct position fora sleeve 46 between the nuts. An angle bracket 41 carried by the brake band itself has a leg extending outwardly and apertured as indicatedfat 48 to ride over the sleeve 46. When thebrake band is in released position, as seen in Figure3,` the extended leg of the bracket 41 abuts the nut 45 and prevents further release movement of thev brake band. When the brake band tightens; around the drum 6 by virtue of a tendency of` the" drum to rotate in the opposite direction, the angle` bracket 41 will move up along the sleeve V46 sub-r stantially to the position seen in Figure 4.- f

When the braking means are installed, they must of course be adjusted for optimum operation. The preferred form of making the adjust-v ment includes first pressing the brake shoeIS firmly against the brake drum 6 and then tightf` ening the nut I6 on the Ybolt I5 to nx the shoe; relatively to the furcations II and I2 of the `arm` l1. The set screw I0 on the anchor bracket` 9 is in the position seen in Figure 3 when .the brake is released. After that, the stop boltmay be adjusted so that there is a relatively great clearance between the nut 45 and the bracket'arm 41 with` the brake bandl just hugging `the brake drum. Then, the drum is rotated back and forthrwhile,r this dimension is decreased until the brake'fl0cl; s..Y

` seen in the drawings.

in the normal direction, the braking mechanism In the iinal setting, the clearance between `the bracket leg and the nut` 45 should be a few eighths inch with the brake locked, say three-eighths for operation. a

One feature of` the braking mechanism above described should be distinctly noted., This isa difference in moment orleverage arms between each of the ends of the brake b-and and thepivot point of the plates 25A and 26. It will be seen that the bolt 3| is much closer to the bolt I5 than is the shaft 3T. This difference in moment arIns` `causes a raising of the arm l upon a tendency of fthe brake drum 6 to rotate in the, opposite direction, and a lowering of that arm when the.

.brake drum starts itsnormal direction of rotation.

In operation, the present invention is extremely simple' and yet` highly effective.

Assuming that theshaft l together with the brake drum 6 are turning counter-clockwise as seen in the drawings so that the conveyer 4 is actively elevating material, upon a sudden cutting olif of the motive power,

l the weight of material upon the conveyer will tend to rotatethe shaft l and the brake drum 6 in the opposite direction, namely, clockwise as While operation continues will have the `position seen in Figure 3, the brake shoe being olf the drum, and the brake band hug` ging the drum to a sucient extent to provide ,enough `friction to insure locking cf thefbrake pand upona tendency toward reverse movement. As soon as the motive power is cut off, and the brake drum 6 tends to rotate in the opposite direction, there will be anl upward pul1 by the band` `loop 28 .upon the bolt 3l, and a corresponding release, if not a slight downward pressure, upon the bo`lt`35 associated with the opposite end of the band. Ine upward pull on the bolt 3l results in elevating the arm l together y'with its furcations l and lz yproviding a dual result, namely a tightening of the brake band around the brake drum,

and the elevation of the brake snce intocontact with the drum. With the parts arranged as above describedit will be noted that the reaction .tothe pull on tlle band is a pressure ol'` the shoe against tne drum. ln other words, both the active and a reactive forces are converted into positive braking l en'ort. Ratner `than provide merely` a pull upon `the brake band to tighten it around the drumwith tne reaction to `that purl carried bythe frame of tlle machine, the reaction is converted into braking eiIort by way or tneorake snoe `is so that there is ootn `a greater braking action and a considerably .lesser load on .the machinerame. a 'this 1s lilglily advantageous especially in portable units o1 iignt construction. 'ljne only load upontne arm `l is a tension load. with this arrangement, it is 4only necessary outside oi the connection of `the ,drum u to the shalt l to make asmgle` point concrank plates 25 and 26 `from the position seen in Figure 4 to the position seen in Figure 3and a consequent dropping of the arm 'l upon the upper end of the set screw l0, thusreleasngathe brake l inch for example. rLlie mechanism is then ready release movement of the band is limited by virtue of the protruding leg of the bracket 41 abutting the `nut 45 on the stop bolt 4l. Suiicient hugging of the brake drum is thereby still maintained to insure a positive acting ofthe brake mechanism again upon a` tendency of the brake drumwto a l rotate in the reverse direction.V `The weight of the parts themselves furnishsuflicient drag that fwhen the mechanism is reversed due to the reversal of the conveyor or the elevator, the setting of the brake is readily actuated. More weight may be incorporated in the parts to eiect this-` i e i result, if desired. l

From the foregoing, `it is apparentlthat I have 1 provided a highly ecient and yet light-weight differential backstop braking mechanism in which the brake load is entirely divorced from the `frame of the machine, and the reaction to the tighten,- ing of the brake band is utilized and converted into additional braking effort by Wayof the brake `1 pended claims.

'4o l vating machine, a brake drum on a shaft of the shoe. Thus, the machine frame carries only a torque load. It will further be noted, that the combinationof the brake band and the brake.

shoe acting upon the drum provides a considerable additional ,l amount of braking effort, and this ishighly desirable especially with light ex- 1 ternal loads, and relatively light equipment. It Will 'also be appreciated'that the mechanism is simple in construction, highly durable, andeconomical to manufacture and use. l

It will, of course, be understood that various l details of construction lmay bevaried through `ai wide range without departing from the principles of this invention and it is, therefore, not'the purpose to limit the patent granted hereonother Wise than necessitated by the `scope'of the ap- I claim as my invention: 1. In an automatic backstopbrake for an elemachine, a freely projectinglsupporting arm piv`` of the band when thedrum tends to turn oted near one end to the frame of the machine,

a brake shoe pivotally connected to the free `portion of lsaid-arm, a brake band around said drum, a bell crank member carried by said arm with its elbow pivoted on the same axis as the brake l shoe, the ends of said band `being connected to` `said bell crank memberon opposite sides of the pivot point but at diierent distances therefrom,` means to limit the pivotal movement of said arm away from said'drum, andmeans to limit the release movement of said band when the drum rotates in a forward direction to maintain sufcient friction to automatically cause a locking .in a

' 2. In an automatic backstop brake for a machine shaft, a brake drum on the shaft, an autol .matically movable supporting arm pivotally supported adjacent the drum, a brake shoe pivot-ally connectedto said arm, a brakeband around said l drum, and a member carried by said arm with a portion pivoted on the same axis as the brakel shoe, the ends of said band being connected to` said member on opposite sides of the pivot point but at different distances therefrom so las to insure automatic locking of the band when the drum tends to turn in a reverse direction and movement of the brake shoe into with the drum.

shoe. The band,` of course, also releases and the l braking contact PAULA. SMITH. l 

